Advantages of tooth brushing with the usage of mechanical toothbrushes are well-known. Mechanized (also called electrical) toothbrushes usually comprise typical units: a handle with a motor, a neck and a head with movable bristle holders, and a mechanism, driving the bristle holders into movement, which units are successively arranged along the longitudinal axis of the brush.
Mechanical toothbrushes with bristle holders rotating along the longitudinal axis of the toothbrush have a simplest design (U.S. Pat. No. 4,163,300). A head of such a toothbrush is made as a protective screen opened on one side, whereon a movable bristle holder is arranged. The movable bristle holder is produced as a rotating shaft with radially extended bristles or bunches of bristles, forming a brush, which bristles are fixed along the whole shaft. The rotating shaft is directly joined with a motor shaft. The main deficiency of such head is that, during rotation of the bristle holder, a reactive torque appears in the handle, which torque should be compensated with a handle held in the fingers that makes the toothbrush very inconvenient in usage.
This deficiency is absent in the heads of other toothbrushes (U.S. Pat. No. 5,864,911), having two parallel elastic brush holders rotating in the opposite directions, which brush holders are installed inside the protective screen. Shafts of the holders are joined with a motor by flexible shafts through a system of tooth wheels. The toothbrush is intended for simultaneous tooth brushing on both sides. For this purpose, bushes are mounted at some distance from each other with a possibility of change of this distance at the expense of the elastic holders. The deficiency of the toothbrush is that it is possible to clean a separately standing tooth effectively, but during the cleaning a row of teeth the contact between the bristle surface and the teeth surface is not tight enough, especially at those sections of the jaw, which have an arched form.
A mechanized toothbrush with holders rotating along the longitudinal axis and intended for tooth brushing on one side is also known (EP0488971). The toothbrush holders are also formed as two parallel shafts with a radial arrangement of bristles. The holders are arranged in relation to each other at a distance slightly exceeding the length of the bristles in such a way that the bristles of the holders overlap each other. The holders rotate in the opposite directions driven by a set of gear teeth arranged together with a motor in the handle. A problem of hermetical sealing of the drive is solved in such toothbrushes, the water tightness is provided by sealing the rotating shafts.
The main deficiency of the toothbrush as well as of all analogous toothbrushes with a brush-shaped bristle holder is the following. A rod-shaped holder of the toothbrush has a very high density of bristles immediately near the rod to provide a sufficient density of the brushes near their ends. Food residues and contaminants caught by bristles under the action of centripetal forces are accumulated between the bristles in the area of increased density of bristles. It is very difficult to wash such a toothbrush. It becomes unsuitable for usage quickly because of the crossing bristles. This significant deficiency didn't allow for widespread use of such toothbrushes.
There is known a toothbrush without a mechanical drive, in which a manual longitudinal displacement of the toothbrush is converted into a rotational movement of bristle holders (RU2240714). The toothbrush contains numerous rotary bristle holders mechanically joined for moving together with the handle. Each such holder is formed as a wheel with radially exposed bristles. The wheels are installed on axles capable of rotation. The axles are disposed in a plane parallel to the plane of contact with the teeth and at an angle to the longitudinal axis of the toothbrush. This angle is in the range of 15-75 degrees. For such an inclined arrangement of the wheel axles in relation to the toothbrush movement, friction of the bristles with the teeth leads to rotation of the wheels, and an ordinary cleaning movement ‘from-side-to-side’ creates a secondary effect of tooth brushing ‘from-top-to-bottom’. This toothbrush relates to manual ones and doesn't have a drive mechanism of bristle holders, and in this regard there is no necessity in hermetic sealing.
There are known mechanical toothbrushes with an oscillatory or rotational movement of bristle holders of a different shape about an axis perpendicular to the plane of the brushing part of the toothbrush (for example, RU2270638, WO2004/080330, WO 2004093718, etc.).
Toothbrushes with a reciprocal movement of holders along the longitudinal axis (WO03/103531) are also known. For increase of the cleaning efficacy, several holders oscillating in an anti-phase are used, as shown in FIG. 6B in Patent RU2318471. Such toothbrushes have a low cleaning efficiency of tooth brushing conditioned by the movement of bristles across the teeth. It is known, that the best results are achieved during the tooth brushing by moving the bristles from top to bottom that helps removing food residues remaining in the slots between neighbour teeth, therefore the mechanical movement in electrical toothbrushes is an object of modern inventive and designing activity.
For the last years many various types of mechanical toothbrushes with a complicated movement of bristle holders in different planes have appeared (U.S. Pat. No. 5,070,567, RU 2300344 and etc.) However, the most effective tooth brushing has been achieved therein with the aid of more complicated, expensive, and inefficient drive mechanisms.
There have appeared mechanical toothbrushes, having bristles, which imitate a movement produced by the hand brushing made from-top-to-bottom (RU 2314775, FIGS. 2 and 3). Three bristle holders are made therein in the form of blocks projecting out of the toothbrush head body opened on one side. The body performs a function of the protective screen. The holders are capable of accomplishing angular oscillatory movements about an axle mounted in the head body parallel to the longitudinal axis of the brush. The neighbour holders carry out a movement in the opposite directions. This toothbrush is considered a closest related art device, herein further called a ‘prototype’.
The prototype brush includes bristle holders having cams mounted in the lower parts thereof and a drive mechanism of a linear type, having a head area with a curved cam slot arranged therein, which cam slot interacts with the cams. In another embodiment of the prototype, a drive shaft is curved in the area of the brush head, while forming a cam area, and a lower end of each holder is made with a slot interacting with this curved cam area of the drive shaft.
In such toothbrushes there is a typical problem of hermetic sealing of the drive mechanism against water and toothpaste, which lead to failures of the toothbrush in case of penetration of water and toothpaste inside the brush head. The linear drive used in the toothbrush is not rigid enough and limits the transmission of power required for an effective tooth brushing. Besides, the drive mechanism limits a turn angle of the holders, and the resultant movement is not sufficient for an effective tooth brushing. The projecting parts of the bristle holders, moving towards each other, create a danger of pinching of soft tissues of the oral cavity. The presence of three holders moving in the opposite directions doesn't provide a proper compensation of the reactive torque, which is passed to the consumer's fingers.
Therefore, the task of creating a mechanized toothbrush with parameters desirable by the consumer, including simplicity and reasonable costs, still remains actual.